I finally got the 8266 in the mail, but can't get it to respond to "AT\r\n" (or AT\r, or AT\n, for that matter). I powered it with two alkaline AA batteries (which gives 3.2V to the circuit according to my scope), pulled the chip select pin up to VCC with a 3K resistor, and connected the GND, RX and TX pins to the GND, TX and RX pins of a TTL-level serial unit (BrainLink) set to 115200,8,N,1.

The red LED is on. The blue LED is faintly glowing. But I am not reading any response to the "AT\r\n". I hooked up an oscilloscope, and there is data being sent to the 8266's RX pin, but the 8266's TX pin is showing a constant +3V (I've also seen a constant +0.88V in some experiments).

I tried removing the pullup, or replacing it with a short, but no luck.

you don't need a resistor to bring CH_PD to VCC. i never use this, you should try it without.when I plug it in to the computer to re-program, i only use the RX/TX on the USB TTL cable. and i connect the GND to GND on arduino and CH_PD+VCC to 3V3 on arduino on another usb port. no resistors.. i was even succesfull sometimes with just using the USB TTL cable alone with the 3V3 and GND pins on it, no arduino necessary. but not always, i usually keep switching back and forth between the two connection methods if there is an error.. when you say "can't get it to respond to "AT\r\n" (or AT\r, or AT\n, for that matter)" is this after the initial setup? are you not even able to re-program it?

If I configure the 8266 module to connect to my home WiFi, will it afterwards automatically connect each time it's powered up, or does some serial command need to be sent for it each time to connect?

If it connects automatically on powerup, then one can use it as a super-simple wireless sensor (with significant latency, but that's irrelevant for my application). I'm thinking of using it in conjunction with a Leakfrog water leak detector. The idea is that I would wire 8266 modules to Leakfrog units, so that when a water leak is detected the 8266 is powered up, and connects to WiFi. Some other device running on my network (e.g., an old Android phone or tablet, or maybe a router with custom firmware) will be polling the network and will email and text me to tell me which 8266 module has powered up, and will again email and text when the module has powered down.

But if the 8266 requires a serial command to connect, then a microcontroller is needed to generate that serial command, and that complicates the hardware.

Sounds great! I want to run it without any processor attached--just have it fire up when the signal fires, and then have something else on the WiFi network pick up the IP address. This way, the costs per unit are low (I want to do four units) and it's real simple.

something called an SDK attachment for the ESP, which i believe eliminates the need for an arduino.. i don't know what it is exactly, i'm not experienced enough.. you should check out the above useful links for sure, especially the forum !!

i'm going to say that it is more like 3-5ms when it comes to uploading to thingspeak.. on the data sheet it mentions 1-2ms from boot up to send data BUT there are lots of obstacles here. i'm sure you can cut the time down to 1-2ms if you didn't use thingspeak but maybe your own server?! it connects to the wifi network only 1 time as well, only at boot up. afterwards it stays connected until turned off.

Another question: If you power up the device out of the box, without any setup, does it show up as a hotspot? I saw one writeup that suggested they do that, and if so, it would help with troubleshooting. (I.e., if it isn't showing up as a hotspot, it's probably defective.) And it would mean that it could be useful for simple 0-1 sensor communications without ANY serial communications with it ever--since one could have another device detect if the hotspot is up.

if your module is pre-set to AT+CWMODE=3 it should show up as an access point on your phone right away, no setup necessary. usually they are sent as AT+CWMODE=2 however.

=1 is STA

=2 is AP

=3 is both..

but either way you would have to connect to it with a usb ttl cable to list your network address first and then connect to it. it needs to know your SSID,PASS.. I always check with my phone to see if it shows up under wireless networks, it always has showed up..hope this helps